1. Technical Field
This invention pertains generally to the field of phenothiazine compounds, and more particularly to certain stably reduced phenothiazine compounds, specifically, certain 3,7-diamino-10H-phenothiazine (DAPTZ) compounds, for example, N,N,N′,N′-tetramethyl-10H-phenothiazine-3,7-diamine bis(hydrogen chloride) and N,N,N′,N′-tetramethyl-10H-phenothiazine-3,7-diamine bis(hydrogen iodide). These compounds are useful as drugs, for example, in the treatment of tauopathies, such as Alzheimer's disease, and also as prodrugs for the corresponding oxidized thioninium drugs (for example, methylhioninium chloride, MTC).
2. Background
A number of patents and publications are cited herein in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Each of these references is incorporated herein by reference in its entirety into the present disclosure, to the same extent as if each individual reference was specifically and individually indicated to be incorporated by reference.
Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise,” and variations such as “comprises” and “comprising,” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a pharmaceutical carrier” includes mixtures of two or more such carriers, and the like.
Ranges are often expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment.
Conditions of dementia are frequently characterised by a progressive accumulation of intracellular and/or extracellular deposits of proteinaceous structures such as β-amyloid plaques and neurofibrillary tangles (NFTs) in the brains of affected patients. The appearance of these lesions largely correlates with pathological neurofibrillary degeneration and brain atrophy, as well as with cognitive impairment (see, e.g., Mukaetova-Ladinska, E. B. et al., 2000, Am. J. Pathol., Vol. 157, No. 2, pp. 623-636). Methylhioninium chloride (MTC) and other diaminophenothiazines have been described as inhibitors of protein aggregation in such diseases, that is, diseases in which proteins aggregate pathologically (see, for example, WO 96/30766 and WO 02/055720).
Methylhioninium chloride (MTC) is currently used to treat methemoglobinemia (a condition that occurs when the blood cannot deliver oxygen where it is needed in the body). MTC is also used as a medical dye (for example, to stain certain parts of the body before or during surgery); a diagnostic (for example, as an indicator dye to detect certain compounds present in urine); a mild urinary antiseptic; a stimulant to mucous surfaces; a treatment and preventative for kidney stones; and in the diagnosis and treatment of melanoma.
MTC has been used to treat malaria either singly (see, e.g., Guttmann, P. and Ehrlich, P., 1891, “Uber die wirkung des methylenblau bei malaria,” Berl. Klin. Woschenr., Vol. 28, pp. 953-956) or in combination with chloroquine (see, e.g., Schirmer, H., et al., 2003, “Methylene blue as an antimalarial agent,” Redox Report, Vol. 8, pp. 272-275; Rengelshausen, J., et al., 2004, “Pharmacokinetic interaction of chloroquine and methylene blue combination against malaria,” European Journal of Clinical Pharmacology, Vol. 60, pp. 709-715). Malaria in humans is caused by one of four protozoan species of the genus Plasmodium: P. falciparum, P. vivax, P. ovale, or P. malariae. All species are transmitted by the bite of an infected female Anopheles mosquito. Occasionally, transmission occurs by blood transfusion, organ transplantation, needle-sharing, or congenitally from mother to fetus. Malaria causes 300-500 million infections worldwide and approximately 1 million deaths annually. Drug resistance, however, is a major concern and is greatest for P. falciparum, the species that accounts for almost all malaria-related deaths. Drugs or drug combinations that are currently recommended for prophylaxis of malaria include chloroquine/proguanil hydrochloride, mefloquine, doxycycline, and primaquine.
MTC (under the name Virostat®, from Bioenvision Inc., New York) has shown potent viricidal activity in vitro. Specifically Virostat® is effective against viruses such as HIV and West Nile Virus in laboratory tests. West Nile virus (WNV) is a potentially serious illness affecting the central nervous system. The large majority of infected people will show no visible symptoms or mild flu-like symptoms such as fever and headache. About one in 150 will develop severe symptoms including tremors, convulsions, muscle weakness, vision loss, numbness, paralysis, or coma. Generally, WNV is spread by the bite of an infected mosquito, but can also spread through blood transfusions, organ transplants, breastfeeding or during pregnancy from mother to child.
Virostat® is also currently in clinical trials for the treatment of chronic Hepatitis C. Hepatitis C is a viral infection of the liver. The virus, HCV, is a major cause of acute hepatitis and chronic liver disease, including cirrhosis and liver cancer. HCV is spread primarily by direct contact with human blood. The major causes of HCV infection worldwide are use of unscreened blood transfusions, and re-use of needles and syringes that have not been adequately sterilized. The World Health Organization has declared hepatitis C a global health problem, with approximately 3% of the world's population infected with HCV and it varies considerably by region. The prevalence in the US is estimated at 1.3% or approximately 3.5 million people. Egypt has a population of approximately 62 million and contains the highest prevalence of hepatitis C in the world, estimated at over 20% of the nation's approximately 62 million people.
MTC, when combined with light, can prevent the replication of nucleic acid (DNA or RNA). Plasma, platelets and red blood cells do not contain nuclear DNA or RNA. When MTC is introduced into the blood components, it crosses bacterial cell walls or viral membrane then moves into the interior of the nucleic acid structure. When activated with light, the compound then binds to the nucleic acid of the viral or bacterial pathogen, preventing replication of the DNA or RNA. Because MTC can inactivate pathogens, it has the potential to reduce the risk of transmission of pathogens that would remain undetected by testing.
Oral and parenteral formulations of MTC are commercially available in the United States, usually under the name Urolene Blue®.